alkylationof p-alkoxyphenols



Patented Nov. 4, 1952 ALKYLATION OF p-ALKOXYPHENOLS Robert H. Rosenwald,Western Springs, Ill., as.- signor to Universal Oil Products Company,Chicago, 111., a corporation of. Delaware No Drawing. Application June30, 1950, Serial N0. 171,539

This invention relates to the alkylation of p-alkoXtphenols and moreparticularly to a novel method for producing high yields of 2-tert.-alkyl-4-alkoxyphenol and low yields of. 3-tert.- alkylF-l-alkoxyphenol.Inthe alkylation of p-alkoxyphenol'with a tertiary alcohol, the productconsists of a major proportion of 2-tert.-alkyl-4-alkoxyphenol, a lesserproportion of 3-tert.-alkyl-4Fall;oxyphenol, as well as varying amountsof 2,5-di-tert.-alkyl i-alkoxyphenol. For certain uses the 2-tert.alkyl-d-alkoxyphenol is very desirable, while the ,3tert.-alkyl-4-alloxyphneol is undesirable. For example, in the preparation of aninhibitor to retard oxidative deterioration of food products, 2 -tert.-butyl -4 methoxyphenol is considerably more p ent than t e 3 -isomer.Ther fo it is important to produce increased yields of the 2-isomer withdecreased yields of the 3-isomer. A159. ,the2,5-di-tert.-butyl-.4-methoxyphenol is not as satisfactory as is the2-tert.-butyl-4- methoxyphenol and it is likewise desirable to reducethe yields of the dialkyl compound to a minimum. The present inventionoffers a novel method for accomplishing these results.

In one embodiment the present invention relates to a method forproducing high yields of 2-tert.-alkyl-4-alkoxyphenol and low yields of3-tert.ra1kyl-4-alkoxyphenol which comprises reacting .p1alkoxyphenolwith a tertiary-al oh l n a ratio of at least 2 rnols of -p=alkoxyphenolper mol of tertiarywalcohol at a temperature of not more than about 175C.

' in a specific embodiment the present inventiQnF relates to a methodfor producing high yields of 2-tert.-butyl-4-methoxyphenol and lowyields of 3vtert.-butyle4emethoxyphenol and 2,5-

- di-tert. -butyl-(i-methoxyphenol, which comprises reactingp-methoxyphenol with tart-butyl-alcohol'in a ratio of from about 2 toabout 10 mols of'p-m'ethoxyphenol per molof tert..-butyl-alcohol at atemperature of from about 125to about 175 C. in the presence of asilica-metal oxide catalyst. As hereinbefore set forth, the presentinvention is directed to a novel method for producing high yields ofdesired 2-.-ter t.-alkyl-4-alkoxyphenols and low yields of the undesired3-tert.-alkyl-4- alkoxyphenols and 2,5-di-tert.-alkyl4-alkoxy- .phenols-These improved results are obtained by the use of selectedconcentrations of reactants and at selected operating conditions.

As an essential feature of the present invenion, t e, r t f p akoxyphenol to tertiary- 12 Claims. (Cl, 260-613) 2 to 10 mols ofpealkoxyphenol per mol of tertiary-alcohol. It has been found thatthese. se lected concentrations, in conjunction with the use ofselectedv temperature conditions, result in the production of a higheryield of the desired 2-isomer with lower yields of the undesired3-isomer and dialkylated product.

Another essential feature of the present invention is the use of atemperature of riot more than about 175 C. and, when using the preferredcatalyst, the temperature is within the range of from about 125 to about175 C, It has been found that the use of this temperature range, inconjunction with the selected molar concentrations of reactants, resultsin higher yields of the desired 2-isomer and lower yields ,of theundesired 3-isomer and dialkylated product.

A preferred final p odu t pr s s te.r butyl.-4..-methoxyphenol and, forits preparation, p-methoxyphenol is reacted with tert.-butyl -.alcoholunder the conditions hereinbefore set forth. When othertert.-.-alkyl-alkoxyphenols are desired, the reactants will be selectedto produce the desired compounds. Thus, in place of 4- methoxyphenol,4-ethoxyphenol, 4-propoxyphenol, 4-butoxyphenol, 4- -pentoxyphenol, etc.may be employed. Similarly, in place of tert.-butyle alcohol,tert.amyl-alcohol, tert.-.heptyl-.alcohol, tert.-octyl-alcohol, etc. maybe utilized.

The reaction of p-alkoxyphenol with tertiaryalcohol is readily effectedin the presence of a suitable catalyst. A preferred catalyst comprisessilica-metaloxide, either synthetically prepared or nat all o currin Aparticularly preferred catalyst comprises silicaealumina which may besynthetically prepared or may comprise naturally occurringaluminum-silicates such as Filtrol, Tonsil, etc. Other suitable metaloxide catalysts include silica composited with one or more of the oxidesof magnesium, zirconium, thorium, titanium, molybdenum, tungsten,manganese, etc. It is understood that the various catalysts are notnecessarily equivalent and also that other suitable catalysts,particularly acids such as phosphoric acid, sulfuric acid, eta, eitherin liquid state or composited with a suitable supporting component, maybe utilized but not necessarily with equivalent results. In general, thelast mentioned catalysts are utilized at a lower temperature which maybe within the range of 50 to 100 C. or more.

The preferred silica-alumina catalyst is synthetically prepared and maybe manufactured by separate, successive or co-precipitation methods.

,QQhOl should e i h the ran e of fr m about In one method a suitableacid, such as sulfuric acid, is reacted with a sodium silicate solution,such as water glass, to form silica gel. When spherical catalysts aredesired, the mixture of acid and water glass are dropped through asuitable orifice onto a rotating disk and therefrom into a suitablesuspending medium, such as mineral seal oil, Nujol, etc. and maintainedtherein until the silica gel sets into firm spheres. Usually the spheresare transferred from the forming zone by means of a layer of waterdisposed beneath the oil layer, and the spheres are washed to removealkali metal ions. The spheres are then composited with alumina bysuspending the same in a suitable aluminum salt solution such as that ofaluminum chloride, aluminum nitrate, aluminum sulfate, etc., aluminumhydroxide being precipitated by the addition of a suitable basicreagent, after which the composite is dried at a temperature of fromabout 200 to about 500 F. and calcined at a temperature of from about800 to about 1200" F. The amount of alumina in the catalyst will rangefrom about 5 to about 20% by weight and generally is within the range offrom about 8 to about 12% by weight, the remainder being composedsubstantially of silica.

The alkylation reaction may be effected in either a batch or acontinuous flow process. In a batch type operation, the reactants andcata: lyst are introduced into a reaction zone equipped with stirring orother suitable means for effecting intimate contact of the catalyst andreactants. The desired heating may be applied to the reactants and/orreaction zone .by well known means. In a continuous type operation, whenemploying a solid catalyst, the catalyst is disposed in the reactionzone and the reactants, at the desired temperature, are passed intocontact with the catalyst, in either upward or downward flow. When usinga liquid catalyst and continuous flow operation, a reaction zoneequipped with stirring or other suitable means is employed. Another typeof operation is the suspensoid type of operation in which the catalystis carried into the reaction zone by means of one or more of thereactants or by means of an inert carrying medium. Another type ofoperation includes the fluidized type process in which the reactants andcatalyst are maintained in a state of turbulence under hindered settlingconditions in the reaction zone. The pressure to be employed will dependupon the type of operation to be utilized and will vary from atmosphericto 1000 pounds or more per square inch.

The products from the above reaction may be treated in any suitablemanner such as by fractionation, solvent extraction, etc. to separateunreacted alkoxyphenol which preferably is res...

EXAMPLE I p-Methoxyphenol was reacted with tertbutyl-alcohol in acontinuous type flow operation utilizing a silica-alumina catalyst at atemperature of C. and a pressure of 250 pounds per square inch. The molratio of methoxyphenol to tert-butyl-alcohol was varied as shown in thefollowing table. The table indicates the weight per cent of the 2- and3-isomers in the monobutyl fraction.

Table 1 Molar ratio p-methoxy- Wt. Per- Wt. Por- Run N0. phenol tertcentof cent of butyl- 2-isomer 3-isomer alcohol The results reported in theabove table are the averages of at least two different run periods.

From the above data it is apparent that, at a temperature of 150 C., theuse of a molar ratio of p-methoxyphenol to tert.-butyl-alcoho1 of 2gives a considerably greater yield of the desired 2-isomer than does theuse of a lower molar ratio of the reactants.

EXAJWLE II Table 2 Molar ratio p methoxy Wt. Per- Wt. Per Wt. Per- RunNo. phenol cent of cent of cent of tert-butyl 2-isomer 3-isomer dibutylalcohol The results reported in the above table are the averages of atleast two different run periods.

From these data it is apparent that the use of a temperature of C. and amolar ratio of 2 and above results in high'yields .of the desiredZ-isomer, low yields of the undesired 3-isomer and very small amounts ofthe undesired dibutyl compounds.

- EXAMPLE III In contrast to the above, runs made in the same manner asdescribed in Example I but utilizing a temperature of 200 C. gave loweryields of the desired 2-isomer as indicated in the data in the followingtable.

Table 3 e Molar ratio p-methoxy- Wt- Per- Wt. Per- Run N o. I phenol:tertcent of cent of butyl-'. 2-isomcr 3-isomer alcohol t 67:1 75 25 I 1.1:1 75 25 1. 5:1 74 26 2:1 74 26 From the above data it is seen that atemperature of 200 C. is undesired in that it produces only 75% of thedesired 2-isomer even when utilizing a. molar ratio of 2:1 ofp-methoxyphenol to tert.-butyl-alcohol.

The examples in the above data clearly show that the use of atemperature below 175 C. and a molar ratio of p-methoxyphenol totert.-butylalcohol of above 2 is critical in the production of highyields of the desired 2-tert.-butyl-4-methoxyphenol and low yields ofundesired 3tert.- buty1-4-methoxyphenol and undesired2,5-ditert.-butyl-4-methoxyphenol.

I claim as my invention:

1. A method for producing high yields of 2- tert.-alkyl-4-alkoxyphenoland low yields of 3- tert.-alkyl-4-alkoxyphenol which comprises reactingp-alkoxyphenol with a tertiary-alcohol in a ratio of at least 2 mols ofp-alkoxyphenol per mol of tertiary-alcohol at an alkylating temperatureof not more than about 175 C.

2. A method for producing high yields of 2- tert.-alkyl-4-alkoxyphenoland low yields of 3- tert.-alkyl-4-alkoxyphenol which comprises reactingp-alkoxyphenol with a tertiary-alcohol in a ratio of at least 2 mols ofp-alkoxyphenol per mol of tertiary-alcohol at an alkylating temperatureof not more than about 175 C. in the presence of a silica-metal oxidecatalyst.

3. A method for producing high yields of 2- tert.-alkyl-4-alkoxyphenoland low yields of 3- tert.-alkyl-4-alkoxyphenol which comprises reactingp-alkoxyphenol with a tertiary-alcohol at an alkylating temperature ofnot more than about 175 C. in the presence of a silica-alumina catalyst.

4. A method for producing high yields of 2- tert.-butyl-4-methoxyphenoland low yields of 3- tert.-buty1-4-methoxyphenol which comprisesreacting p-methoxyphenol with tert.-butyl-alcohol in a ratio of at leasttwo mols of p-alkoxyphenol per mol of tert.-butyl-alcohol at analkylating temperature of not more than about 175 C.

5. A method for producing high yields of 2- tert.-butyl-4-methoxyphenoland low yields of 3- tert.-butyl-4-methoxyphenol which comprisesreacting p-methoxyphenol with tert.-butyl-alcohol in a ratio of at leasttwo mols of p-alkoxyphenol per mol of tert.-butyl-alcohol at analkylating temperature of not more than about 175 C. in the presence ofa silica-metal oxide catalyst.

6. A method for producing high yields of 2- tert.-buty1-4-methoxyphenoland low yields of 3- tert.-butyl-4-methoxyphenol which comprisesreacting p-methoxyphenol with tert.-butyl-alcohol in a ratio of at leasttwo mols of p-alkoxyphenol. per mol of tert.-butyl-alcohol at analkylating 5 temperature of not more than about 175 C. in the presenceof silica-alumina catalyst.

7. A method for producing high yields of 2- l 6tert.-butyl-4-methoxyphenol and low yields of 3-tert.-butyl-4-methoxyphenol and 2,5-di-tert.- butyl-4-methoxyphenol,which comprises reacting p-methoxyphenol with tert.-butyl-alcohol in aratio of from about 2 to about 10 mols of pmethoxyphenol per mol oftort-butyl-alcohol at a temperature of from about to about C. in thepresence of a silica-metal oxide catalyst.

8. A method for producing high yields of 2- tert.-butyl-4-methoxyphenoland low yields of 3- tert.-butyl-4-methoxyphenol and 2,5-di-tert.-butyl-4-methoxyphenol, which comprises reacting p-methoxyphenol withtert.-buty1-alcohol in a ratio of from about 2 to about 10 mols ofpmethoxyphenol per mol of tert.-butyl-alcohol at a temperature of fromabout 125 to about 175 C. in the presence of silica-alumina catalyst.

9. A method for producing high yields of 2- tert.-alkyl-4-alkoxyphenoland low yields of 3- tert.-alkyl-4-alkoxyphenol which comprises reactingp-alkoxyphenol with a tertiary-alcohol at an alkylating temperature ofnot more than about 175 C. in the presence of a silica-magnesiacatalyst.

10. A method for producinghigh yields of 2- tert.-alky1-4-alkoxyphenoland low yields of 3- tert.-alkyl-4-alkoxyphenol which comprises reactingp-alkoxyphenol with a tertiary-alcohol at an alkylating temperature ofnot more than about 175 C. in the presence of a silica-zirconiacatalyst.

11. A method for producing high yields of 2- tert.-alkyl-4-alkoxyphenoland low yields of 3- tert.-alkyl-4=-alkoxyphenol which comprisesreacting p-alkoxyphenol with a, tertiary-alcohol at an alkylatingtemperature of not more than about 17 5 C. in the presence of asilica-thorium oxide catalyst.

12. A method for producing high yields of 2- tert.-alkyl-4-alkoxyphenoland low yields of 3- tert.-alkyl-4-alkoxyphenol which comprises reactingp-alkoxyphenol with a tertiary-alcohol at an alkylating temperature ofnot more than about 175 C. in the presence of a silica-molybdenum oxidecatalyst.

ROBERT H. ROSENWALD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 23,239 Rosenwald et a1. June6, 1950 2,470,902 Rosenwald May 24, 1949 2,514,419 Schulze et a1. July11, 1950 2,516,152 Schulze et a1. July 25, 1950

4. A METHOD OF PRODUCING HIGH YIELDS OF 2TERT,-BUTYL-4-METHOXYPHENOL ANDLOW YIELDS OF 3TERT,-BUTYL-4-METHOXYPHENOL WHICH COMPRISES REACTINGP-METHOXYPHENOL WITH TERT-BUTYL-ALCOHOL IN A RATIO OF AT LEAST TWO MOLESOF P-ALKOXYPHENOL PER MOLE OF TERT-BUTYL-ALCOHOL AT AN ALKYLATINGTEMPERATURE OF NOT MORE THAN ABOUT 175* C.